You know you've always wondered
If you’re someone who cooks with recipes, it’s likely that at one point you’ve come across a recipe that states explicitly to use a nonreactive bowl to mix something or a pot to cook a sauce. Did you hop on Google? Did you continue to use the one mixing bowl or stockpot you own and hope for the best? Regardless of how you answered, there’s no denying that this is a fairly complex recipe direction, and you should feel confident in your cooking.
“Reactive” and “nonreactive” refer to the type of metal something (usually a bowl or pot) is made of. Iron, aluminum, and unlined copper are reactive metals, which mean that when some foods are cooked or left in one for an extended period of time, the metal particles in the porous vessel can chemically interfere with the ingredients, causing them to turn metallic in flavor. Acidic foods like tomatoes may not taste great if cooked in cast iron pan for hours, unless that pan is perfectly seasoned, but since reactive pans are so good at conducting heat, they’re a great choice for searing meat. Additionally, copper bowls are especially exceptional for whipping cream or egg whites. As tiny copper particles break off, they attach themselves to the protein in the egg whites or cream, and act as an additional stabilizer.
Nonreactive vessels are made with materials like glass, tin (and tin-coated copper), ceramic, stainless steel, and enamel (and enamel-coated cast iron). These materials are ideal for any food, and especially when cooking acid foods like tomatoes, lemon juice, and vinegar for long periods of time, like a tomato sauce. Ultimately, if you’re shopping for new pots and bowls, a solid nonreactive stainless steel set is the best choice